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Toxicological characteristics of particulate matter in an urban environment and their linkage to the source-specific constituents

TOXICOLOGICAL CHARACTERISTICS OF PARTICULATE MATTER IN AN
URBAN ENVIRONMENT AND THEIR LINKAGE TO THE SOURCE-SPECIFIC
CONSTITUENTS
by
Vishal Verma
___________________________________________________________________
A Dissertation Presented to the
FACULTY OF THE USC GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(ENVIRONMENTAL ENGINEERING)
May 2011
Copyright 2011 Vishal Verma

A number of population based epidemiological studies as well as recent toxicological and clinical studies indicate a strong association between particulate matter (PM) exposure and adverse health outcomes. Despite commendable progress in particle-related toxicological research for the last few decades, the exact mechanisms by which PM inflicts health injuries are still largely unknown and constitute a subject of great interest for the scientific community. An increase in the abundance of reactive oxygen species (ROS) in biological systems after PM exposure and the resulting oxidative stress has been hypothesized to be mostly responsible for the initiation of inflammatory cascades.; The core objective of this work is to determine the toxicological characteristics of particulate matter in an urban environment and to investigate their associations with the source-specific particle constituents. This objective has been accomplished by evaluating the oxidative potential of particles collected from various sources such as exhaust tail pipe of the heavy-duty diesel vehicles, wood-smoke and ambient particles in segregation to their primary and secondary sources. The role of semi-volatile organic compounds in the oxidative activity of PM was assessed by their removal using thermodenuder and measuring the resultant oxidative potential by DTT assay. Similarly, the contribution of transition metals was quantified by their chelation using Chelex® chromatography. The use of statistical tools (bivariate and multivariate regression techniques) further supported in identification of the specific PM constituents responsible for major variability in the responses of toxicological assays. The results demonstrate the importance of both semi-volatile (organic compounds) and non-volatile (transition metals) species of particulate matter in stimulating the generation of different oxidizing species in biological systems, measured by DTT and ROS assay. These findings are useful in elucidating the health risks related to the PM exposure from different sources and ultimately in promulgating the effective control strategies to protect public health.

TOXICOLOGICAL CHARACTERISTICS OF PARTICULATE MATTER IN AN
URBAN ENVIRONMENT AND THEIR LINKAGE TO THE SOURCE-SPECIFIC
CONSTITUENTS
by
Vishal Verma
___________________________________________________________________
A Dissertation Presented to the
FACULTY OF THE USC GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(ENVIRONMENTAL ENGINEERING)
May 2011
Copyright 2011 Vishal Verma